Our long-term objective is to develop new therapies for esophageal squamous cell carcinoma (ESCC) that are based on the unique biological characteristics of this malignancy. Our working hypothesis is that tumor cells establish a dominant relationship with stromal cells to control the formation of a primitive 'organ', in which all cellular constituents contribute to tumor cell growth, survival and invasion. We then hypothesize that tumor cell resistance to conventional therapies is due to intrinsic and microenvironmental factors. In preliminary studies we have developed three-dimensional culture models of the normal esophagus and of ESCC tumors that mimic conditions in vivo. These models allow us to dissect the roles for each cell type in a tissue-like context to determine how tumors progress and resist therapeutic drugs. This hypothesis will be pursued by the following interrelated Specific Aims: 1) To determine and define the functional synergy between stromal fibroblasts, endothelial cells, and ESCC cells with a focus upon the interplay between stromal fibroblasts and endothelial cells to nurture the microenvironment for esophageal tumor cells. To that end, tumors represent a finely tuned 'organ' in which the malignant cells dominate to drive activationof fibroblasts for matrix and growth factor production. Activated fibroblasts in turn attract endothelial cell and induce their differentiation for vessel formation and provide positive feedback for the tumor cells. We will analyze the secretion of soluble mediators (eg TGFbeta) and the dynamics of cell-cell interactions that together increase the invasive nature of tumors; 2) We will develop strategies to overcome the strong resistance of ESCC cells to current therapy. We believe that the unusual resistance to drugs is due to both microenvironmental and intrinsic cues. We will target the fibroblast-endothelial axis. In the second strategy, we have identified a proteasome inhibitor, Bortezomib, as very active. We will determine how we can enhance it's efficacy in SCC and plan to use it in combination with radiation and pro-apototic agents. Project 2 is closely integrated with Project 1 (Aims 2 and 3) and Project 3 (Aims 1 and 3), and makes extensive use of the outstanding, cohesive core facilities. RELEVANCE (See instructions): This Project focuses upon how activated fibroblasts impact upon endothelial cells to nurture neo- angiogenesis in the esophageal tumor microenvironment, which is very critial for tumor cell maintenance and growth. New stratagies are being developed to disrupt this axis and understand the role of novel biological modifiers in the tumor microenvironment and in vivo. Success has been achieved already in taking one approach to a Phase Ib clinical protocol _^_